Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
  • G02B27/42—Diffraction optics, i.e. systems including a diffractive element being designed for providing a diffractive effect
  • G02B27/44—Grating systems; Zone plate systems
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
  • G02B27/0025—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for optical correction, e.g. distorsion, aberration
  • G02B27/0037—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for optical correction, e.g. distorsion, aberration with diffracting elements
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
  • G02B27/42—Diffraction optics, i.e. systems including a diffractive element being designed for providing a diffractive effect
  • G02B27/4205—Diffraction optics, i.e. systems including a diffractive element being designed for providing a diffractive effect having a diffractive optical element [DOE] contributing to image formation, e.g. whereby modulation transfer function MTF or optical aberrations are relevant
  • G02B27/4211—Diffraction optics, i.e. systems including a diffractive element being designed for providing a diffractive effect having a diffractive optical element [DOE] contributing to image formation, e.g. whereby modulation transfer function MTF or optical aberrations are relevant correcting chromatic aberrations
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
  • G02B27/42—Diffraction optics, i.e. systems including a diffractive element being designed for providing a diffractive effect
  • G02B27/4272—Diffraction optics, i.e. systems including a diffractive element being designed for providing a diffractive effect having plural diffractive elements positioned sequentially along the optical path
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B5/00—Optical elements other than lenses
  • G02B5/18—Diffraction gratings
  • G02B5/1814—Diffraction gratings structurally combined with one or more further optical elements, e.g. lenses, mirrors, prisms or other diffraction gratings
  • G02B5/1819—Plural gratings positioned on the same surface, e.g. array of gratings
  • G02B5/1823—Plural gratings positioned on the same surface, e.g. array of gratings in an overlapping or superposed manner

Definitions

• the present invention relates to a laminated
• diffractive optical element and particularly to a
• DOEs Diffractive optical elements
• DOEs are nearly always provided with reduced optical powers to be used in optical systems for multicolor lights so as to correct the chromatic
• Japanese Patent No. 3966303 discloses a pickup lens having on its each surface binary step with different heights. This pickup lens sets the height of binary steps on one surface to a value equal to an integral multiple of a wavelength that is not desired to be diffracted through the binary steps and to a value different from an integral multiple of a wavelength that is desired to be diffracted therethrough, thereby diffracting only light of the desired wavelength.
• Japanese Patent Laid-Open No. 9-189892 discloses a displaying optical system including a liquid crystal DOE.
• the displaying optical system performs highspeed time division switching of a wavelength of light from a light source such as R ⁇ G ⁇ B ⁇ R ⁇ ..., and switches parameters of the liquid crystal DOE in synchronization with the time division switching, thereby suppressing generation of aberration.
• a diffraction order of the DOE is +lst order and a focal length thereof is 50mm
• a curvature radius is -28.63mm and the longitudinal chromatic
• R-B aberration of R-B is 0.775mm. Furthermore, description will be made of an example of a reflective DOE that converts an incident angle of 25° into a reflection angle of 60° and whose diffraction order is +lst order and focal length is 50mm. In this DOE, the longitudinal chromatic aberration of R-B increases to 40mm or more.
• the DOEs disclosed in Japanese Patent No. 3966303 and Japanese Patent Laid-Open No. 9-189892 may solve the above-described problem.
• the DOE disclosed in Japanese Patent No. 3966303 is a multi-level zone plate DOE, which may obtain an insufficient diffraction
• liquid crystal DOE disclosed in Japanese Patent Laid-Open No. 9-189892 involves a problem that accuracy of an annular zone interval depends on a size of a pixel cell and a problem that temporal
• the present invention provides a laminated
• the present invention provides as one aspect thereof a laminated diffractive optical element including plural diffraction gratings laminated with each other, the respective diffraction gratings being formed of a same light-transmissive material, and plural reflective films formed on grating surfaces of the respective diffraction gratings, each of the reflective films being disposed between the diffraction gratings.
• Each of the reflective films reflects light in a specific wavelength range and transmits light in a wavelength range different from the specific wavelength range, the specific wavelength ranges for the respective reflective films being different from each other.
• the grating surfaces of the respective diffraction gratings are formed in shapes different from each other according to the specific wavelength ranges for the respective reflective films.
• the present invention provides as another aspect thereof a laminated diffractive optical element including plural diffraction gratings laminated with each other, the respective diffraction gratings being formed of light- transmissive materials different from each other. Grating surfaces of the respective diffraction gratings are formed in shapes different from each other. Refractive indices of the diffraction gratings adjacent to each other in a lamination direction in which the diffraction gratings are laminated have mutually different dispersion
• the present invention provides as still another aspect thereof an optical system including the above- described laminated diffractive optical element.
• FIG. 1 schematically shows a structure of a
• FIG. 2 schematically shows a structure of a
• FIG. 3 schematically shows a structure of a
• FIG. 4 shows an optical system including the
• FIG. 5 is a graph showing a reflectance
• FIG. 6 is a graph showing a reflective diffraction efficiency of the reflective DOE of Example 3 for a wavelength ⁇ ⁇ -
• FIG. 7 is a graph showing transmissive diffraction efficiencies of the reflective DOE of Example 3 for wavelengths X G and ⁇ ⁇ .
• FIG. 8 schematically shows a structure of a
• FIG. 9 schematically shows a structure of a
• FIG. 10 is a graph showing diffraction efficiencies at a grating surface.
• FIGS. 11 and 12 are graphs showing dispersion characteristics of materials used for the transmissive DOE of Example 2.
• FIG. 13 shows an optical system that is Example 5 of the present invention.
• FIG. 14 shows an optical system that is Example 6 of the present invention.
• FIG. 15 is a graph showing dispersion
• FIG. 1 shows a reflective laminated DOE (laminated diffractive optical element) 1 that is a first example
• the DOE 1 is constituted by laminating three diffraction grating laye
• diffraction grating layers are formed of a same light- transmissive medium (material) , and refractive indices ( ⁇ ( ⁇ )) thereof are also equal to each other.
• a dichroic film as a reflective film that reflects light in a first wavelength range is formed on a grating surface 11 disposed between the first layer 21 and the second layer 22.
• a dichroic film as a reflective film that reflects light in a second wavelength range is formed on a grating surface 12 disposed between the second layer 22 and the third layer 23.
• a grating surface 13 is formed as a mirror surface that reflects light transmitted through the first to third layers 21-23.
• This mirror surface may be formed of a reflective film vapor-deposited on a back surface of the third layer 23 or may be formed of a metal plate.
• the reflective films formed on the grating surfaces 11 and 12 are not limited to the dichroic film, and only have to be a film that reflects light in a specific wavelength range (such as the light in the first
• Forming the first to third layers 21-23 with the same material as described above makes the entire DOE 1 thin.
• the first to third layers 21 to 23 are formed of resin
• forming the grating surface 13 that includes the mirror surface on a substrate and then sequentially forming thereon the third layer 23, the dichroic film, the second layer 22, the dichroic film and the first layer 21 can produce the DOE.
• an anti-reflection film may be formed on a light entrance side surface 10 of the first layer 21.
• disposing a transparent substrate further on a light entrance side than the surface 10 and then sequentially forming thereon the first layer 21, the dichroic film, the second layer 22, the dichroic film, the third layer 23 and the reflective film can produce the DOE as a back-surface mirror .
• the grating surfaces 11 and 12 on which the dichroic films are formed and the grating surface 13 on which the mirror surface is formed include gratings formed as grating annular zones having a blazed shape (hereinafter, the dichroic films are also denoted by reference numerals 11 and 12, and the mirror surface is also denoted by reference numeral 13) .
• the annular zones are formed with an annular zone interval set based on a phase difference function calculated so as to provide a required optical power .
• the DOE 1 is assumed to be formed in a flat plate shape as a whole, and an envelope surface of edges of the gratings formed on each of the grating surfaces 11-13 and the surface 10 are assumed to be a plane.
• non-monochromatic light entering the DOE 1 from the surface 10 is transmitted through the first layer 21, and then light in the first wavelength range included in the non-monochromatic light is reflected and diffracted at a predetermined diffraction order by the grating surface 11.
• the reflected and diffracted light is again transmitted through the first layer 21 to exit from the DOE 1 through the surface 10.
• Light in a wavelength range other than the first wavelength range included in the non- monochromatic light is transmitted through the grating surface 11 without being diffracted since the refractive indices of the first and second layers 21 and 22 are equal to each other.
• light in the second wavelength range is reflected and diffracted at the predetermined diffraction order by the grating surface 12, and then is again transmitted through the second layer 22 and the first layer 21 to exit from the DOE 1 through the surface 10 without being diffracted by the grating surface 11.
• light in a wavelength range other than the second wavelength is transmitted through the grating surface 12 without being diffracted since the refractive indices of the second and third layers 22 and 23 are equal to each other.
• the light transmitted through the grating surface 12 and the third layer 23 is reflected and diffracted at the predetermined diffraction order by the grating surface 13, and is again transmitted through the third to first layers 23-21 to exit from the DOE 1 through the surface 10
• the DOE 1 of this example can set, if optimizing the shape of each of the grating surfaces for the
• wavelength range which is desired to be diffracted by that grating surface that is, the specific wavelength range
• the DOE 1 of this example can reduce chromatic aberration. That is, the grating
• surfaces 11 and 12 in the DOE 1 of this example have mutually different shapes according to the specific
• the DOE 1 of this example can optimize the diffraction efficiency at each grating surface in an arbitrary wavelength range, therefore making it possible to ensure a high diffraction efficiency in a limited wavelength range to be reflected and diffracted as shown in FIG. 10.
• reference character IL denotes non- monochromatic light (incident light) that impinges on a certain point on the DOE 1.
• the grating surface 11 reflects and diffracts the light in the first wavelength range including a wavelength ⁇ , and transmits the light in the wavelength range other than the first wavelength range.
• the grating surface 12 reflects and diffracts the light in the second wavelength range
• the grating surface 13 reflects and diffracts the light in the wavelength range transmitted through the grating surfaces 11 and 12 including a wavelength ⁇ 3 .
• Reference characters DLi, DL 2 and DL 3 respectively denote light rays reflected and diffracted at the grating surfaces 11, 12 and 13.
• Reference characters P x , P 2 and P 3 and di, d 2 and d 3 respectively denote annular zone intervals (pitches of the annular zones) P and grating heights d at the incident points of the light rays DLi, DL 2 and DL 3 on the grating surfaces 11, 12 and 1.3.
• annular zone intervals Pi, P 2 and P 3 and the grating heights di, d 2 and d 3 on the grating surfaces 11, 12 and 13 are mutually different on a same incident ray axis along which the light rays DLi, DL 2 and DL 3 trace.
• phase difference function ⁇ is generally expressed as follows:
• the annular zone interval P(r) is expressed as follows :
• the grating heights of the respective grating surfaces so as to become maximum at the wavelengths ⁇ , ⁇ 2 and ⁇ 3 .
• the wavelengths ⁇ , ⁇ 2 and ⁇ 3 are not necessarily required to coincide with the wavelengths when the above-described annular zone intervals are set, and may be appropriate values for wavelength spectra to be reflected at the respective grating surfaces.
• the grating height d is expressed as follows:
• the grating heights di, d 2 and d 3 only have to be set as follows if the wavelengths are ⁇ 3 ⁇ 2 ⁇ ,
• the grating heights di, d 2 and d 3 only have to approximately satisfy the following relationship:
• the diffraction efficiency shown by a vertical axis decreases as a wavelength of diffracted light (shown by a horizontal axis) departs further from a wavelength at which the diffraction efficiency is peak (hereinafter referred to as a "peak wavelength") . Therefore, it is desirable that a spectrum of light entering the DOE have a peak near the peak wavelengths of the respective grating surfaces and be as narrow as possible. For example, using a light source such as a laser and an LED whose peak of the spectrum is near the respective peak wavelengths enables reduction of unnecessary diffracted light. On the other hand, even if the spectrum of the light source is wide, providing plural color filters periodically with respect to pixels of a display element or an image pickup element enables acquisition of similar effects.
• FIG. 2 shows a transmissive laminated DOE 2 that is a second example (Example 2) of the present invention.
• This DOE 2 is also constituted by laminating plural diffraction grating layers (diffraction gratings) each diffracting monochromatic light, which is the same as the DOE 1 of Example 1.
• the DOE 2 has a color correction function for two wavelengths.
• the DOE 2 is constituted by laminating three light- transmissive media including a first layer 41, a second layer 42 and a third layer 43.
• the three light- transmissive media are different from each other, and refractive indices thereof are also mutually different.
• the refractive indices of the light-transmissive media forming the first layer 41, the second layer 42 and the third layer 43 are respectively represented by ni ( ⁇ ) , n 2 ( ⁇ ) and n 3 ( ⁇ ) .
• a grating surface 11 disposed between the first layer 41 and the second layer 42 and a grating surface 12 disposed between the second layer 42 and the third layer 43 are formed as grating surfaces having a blazed
• Light IL including at least light in wavelengths ⁇ and ⁇ 2 enters the DOE 2 through a surface 10, and then exits from the DOE 2 through a surface 14.
• the grating surfaces 11 and 12 and the surface 10 and 14 may be provided with an anti-reflection film.
• a light-transmissive substrate may be disposed further on a light entrance side than the surface 10 or further on a light exit side than the surface 14.
• the light- transmissive substrate serves as a holding member, which makes it possible to thin the layer on the light entrance side or on the light exit side.
• the refractive indices ni ( ⁇ ) and n 2 (A)of the first and second layers 41 and 42 adjacent to each other in a lamination direction in which the first to third layers 41-43 are laminated with each other are at least different from each other for the wavelength ⁇ (one color light) and equal to each other for the other wavelength ⁇ 2 . That is, the first and second layers 41 and 42 have dispersion characteristics such that the following relationships are satisfied:
• ⁇ ⁇ ( ⁇ 2 ) ⁇ 2 ( ⁇ 2 ) ...(9) .
• the grating surface 11 is formed such that an
• annular zone interval Pi and a grating height di can provide a required diffraction power and a required
• the light in the wavelength ⁇ is transmitted therethrough and diffracted in a
• the light in the wavelength ⁇ 2 is transmitted therethrough without being diffracted to enter the second layer 42.
• the refractive indices ⁇ 2 ( ⁇ ) and n 3 ( ⁇ ) of the second layer 42 and the third layer 43 adjacent to each other in the lamination direction are different from each other for at least the wavelength ⁇ 2 (one color light) and equal to each other for the other wavelength ⁇ . That is, the second layer 42 and the third layer 43 have
• the grating surface 12 is formed such that an annular zone interval P 2 and a grating height d 2 ' can provide a required diffraction power and a required
• the light in the wavelength ⁇ 2 is transmitted therethrough and diffracted in a
• the light in the wavelength ⁇ is transmitted therethrough without being diffracted to enter the third layer 43.
• FIG. 11 shows the dispersion characteristics of the light-transmissive media forming the first to third layers 41-43.
• ⁇ is 640nm and ⁇ 2 is 410nm.
• the light-transmissive medium is disposed as a layer further on the light entrance side as the index j is smaller. In this case, it is only necessary that a wavelength
• n j (Xj . ) ⁇ ( ⁇ ⁇ ) ... (11) .
• the DOE has a structure including four layers. Light of the wavelength ⁇ is diffracted by a grating surface between a first layer and a second layer independently, light of the wavelength ⁇ 2 is diffracted by a grating surface between the second layer and a third layer independently, and light of the wavelength ⁇ 3 is diffracted by a grating surface between the third layer and a fourth layer
• Methods for providing the dispersion characteristics required for the respective light-transmissive media include, for example, a method that dopes inorganic nanoparticles into a light-transmissive organic material.
• FIG. 3 shows a specific example of the reflective laminated DOE 1 described in Example 1.
• This DOE 1 is constituted by laminating three layers of diffraction gratings including the first layer 21 to the third layer 23, the layers being formed of the same light-transmissive media.
• the grating surface 11 is formed between the first layer 21 and the second layer 22, the grating surface 12 is formed between the second layer 22 and the third layer 23, and the grating surface 13 is formed on the back surface of the third layer 23.
• a dichroic film is formed on the grating surface 11. This dichroic film reflects and diffracts light in a wavelength range (first wavelength range) from red (R) to infrared. Another dichroic film is formed on the grating surface 12. This dichroic film reflects and diffracts light in a wavelength range (second wavelength range) from ultraviolet to blue (B) . The grating surface 13 reflects and diffracts at least light in a wavelength range of green (G) (third wavelength range) transmitted through the grating surfaces 11 and 12.
• G green
• This structure enables the two dichroic films to independently reflect and diffract the light in the first wavelength range that is a short side wavelength range and the light in the second wavelength range that is a long side wavelength range. Furthermore, this structure enables at least the grating surface that reflects the light in the third wavelength range between the first and second wavelength ranges to diffract that light with a required power.
• this structure only requires to set reflectance characteristics of the two light-entrance side surfaces like a low-pass filter (some nm or less) or a high-pass filter (some nm or more) , that is, does not require to set them like a band-pass filter, which enables simplification of the structure of the dichroic film.
• the grating surface 11 reflects the light in the wavelength range from blue to ultraviolet and the grating surface 12 reflects the light in the
• the first grating surface 11 that reflects the light in the wavelength range from blue to ultraviolet and the second grating surface 12 that reflects the light in the wavelength range from red to infrared are arranged in no particular order from the light entrance side.
• the third grating surface 13 that reflects the light in a wavelength range transmitted through the dichroic films formed on the first and second grating surfaces 11 and 12 may be formed on a side opposite to the light entrance side with respect to the first and second grating surfaces 11 and 12.
• FIG. 4 shows an optical system that forms an image by using a reflective DOE 50 which is decentered, the optical system having a diameter of an entrance pupil of 5mm and an angle of view of 20 degrees. Numerical dat of the optical system is shown below.
• An origin of coordinates is set to a center of the entrance pupil, and an axis passing the center of the pupil and extending in a direction orthogonal to the pupil is defined as a Z axis.
• An axis extending in a direction orthogonal to the Z axis and in a direction along a decentering cross section (meridional cross section) is defined as a Y axis.
• An axis extending in directions orthogonal to the Y axis and the Z axis is defined as an X axis, and ⁇ represents a rotational decentering angle around the X axis.
• This optical system is configured such that an incident angle is larger than a reflection angle.
• a y-z plane is referred to as the meridional cross section and a x-z plane is referred to as a sagittal cross section.
• the phase difference function is expressed as follows:
• Ci -3.75050-10 "3
• Cio -2.77163-10 "14
• the annular zone interval P k ( y ) is expressed as follows based on the expression (4) :
• the incident angle thereof on the DOE is 25° and a distance y from an optical axis of the optical system to an incident point of the principal ray on the DOE is 5.65mm.
• the above-described principal ray exits from the DOE at a reflection angle of 30.65°.
• the annular zone intervals P k on the grating surfaces that reflect and diffract the respective color lights are as follows:
• Grating heights d are as follows:
• dichroic film reflects and diffracts light in the wavelength from ultraviolet to blue, and transmits light in the wavelengths of red and green without
• FIG. 5 shows wavelength dependency of reflectance of P-polarized light when assuming that the wavelength ⁇ ⁇ is 480nm, a refractive index n H of the layer H is 1.7 and a refractive index n L of the layer L is 1.5.
• the reflectance is approximately 0% in a wavelength range of 475 nm or less and approximately 100% in a wavelength range of 575 nm or more.
• FIG. 6 shows a reflective diffraction efficiency of the principal ray of the wavelength ⁇ ⁇ when the incident angle thereof is 45° and the incident point (y) thereof is 3.0mm.
• FIG.7 shows transmissive diffraction efficiencies of principal rays of the wavelengths X G and X R .
• the transmissive diffraction efficiencies are calculated by rigorous coupled wave analysis.
• the reflective diffraction efficiency of the +5th order diffracted light of the wavelength ⁇ ⁇ is 82.39%, and the transmittances of the 0th order diffracted lights of the wavelengths K R and A G are 94.6% and 90.1%, respectively.
• relative diffraction efficiency of the +5th order diffracted light of the wavelength ⁇ ⁇ is 82.39%
• the transmittances of the 0th order diffracted lights of the wavelengths K R and A G are 94.6% and 90.1%, respectively.
• wavelengths A R and A G are less than 0.2%, which means that most of the light of the wavelength ⁇ ⁇ is reflected and diffracted and most of the lights of the other wavelengths are transmitted without being diffracted.
• the intensities of diffracted lights of the wavelength ⁇ ⁇ whose diffraction orders are other than the +5th order are about 1%, such slightly high intensities can be reduced by adjustment of the shape of the grating such as tilting of a grating side face.
• FIG. 8 shows a fourth example (Example 4) as another specific example of the reflective laminated DOE 1 described in Example 1.
• Example 3 forms portions between the grating surfaces by using a single (same) light-transmissive medium to reduce the thickness of the DOE, this example respectively forms diffraction gratings on light-transmissive substrates and combines these diffraction gratings to produce the reflective laminated DOE.
• a reflective DOE in which a dichroic film is formed on a grating surface 11 between layers 21 and 22 formed of a same light-transmissive medium whose
• refractive index is ⁇ ( ⁇ ) is formed on a light-transmissive substrate 30 whose refractive index is ⁇ ⁇ ( ⁇ ), which constitutes a first reflective diffraction unit.
• the refractive index ⁇ ( ⁇ ) may be equal to the refractive index ⁇ ⁇ ( ⁇ ) or may be different therefrom.
• the dichroic film formed on the grating surface 11 reflects and diffracts light of a wavelength A R (R-light) .
• another reflective DOE in which a dichroic film is formed on a grating surface 12 between layers 23 and 24 formed of the same light-transmissive medium whose refractive index is ⁇ ( ⁇ ) is formed on another light- transmissive substrate 30 whose refractive index is ⁇ ⁇ ( ⁇ ), which constitutes a second reflective diffraction unit.
• the refractive index ⁇ ( ⁇ ) may be equal to the refractive index ⁇ ⁇ ( ⁇ ) or may be different therefrom.
• the dichroic film formed on the grating surface 12 reflects and
• Still another reflective DOE in which a dichroic film is formed on a grating surface 13 of a layer 25 formed of the light-transmissive medium whose refractive index is ⁇ ( ⁇ ) is formed on still another light- transmissive substrate 30 whose refractive index is ⁇ ⁇ ( ⁇ ), which constitutes a third reflective diffraction unit.
• the refractive index ⁇ ( ⁇ ) may be equal to the refractive index ⁇ ⁇ ( ⁇ ) or may be different therefrom.
• the grating surface 13 is formed as a mirror surface that reflects and diffracts light of a wavelength ⁇ ⁇ (G-light) .
• the first to third reflective diffraction units are disposed adjacently to each other so as to form air layers 31 therebetween to be laminated with each other.
• the first to third reflective diffraction units may be disposed in contact with each other so as not to form the air layers 31 therebetween to be laminated with each other, as shown in FIG. 9.
• a diffraction power can be set independently for each color light.
• Example 5 Description will be made of a fifth example (Example 5) as still another specific example of the reflective laminated DOE 1 described in Example 1. Although in Examples 3 and 4 the reflective laminated DOE is used alone in the optical system, the reflective laminated DOE may be used in combination with refractive elements or reflective elements.
• FIG. 13 shows an optical system in which the
• This optical system can be used as an image taking optical system of a camera with an image pickup element such as a CCD sensor or a CMOS sensor disposed at a surface 65. Furthermore, this optical system can be used as a displaying optical system of an image display apparatus with a display element such as a liquid crystal panel disposed at the surface 65, the displaying optical system enlarging an image formed on the display element such that the enlarged image can be observed from a pupil 61.
• external light from an entrance pupil 61 enters the prism element 60 through its surface 62, is reflected by a backside of a surface 63 to exit from the prism element 60 through its surface 64, and then is introduced to the image pickup element disposed at the surface 65.
• the surface 63 is provided with the DOE.
• This example has a relationship that a reflection angle is larger than an incident angle to reduce a thickness and a size of the prism element 60.
• Numerical data of the above-described optical system is shown below.
• a coordinate system in the numerical data is the same as that described in Example 3.
• the optical system has .an angle of view of ⁇ 20 degrees and a diameter of the entrance pupil of 5mm.
• a phase difference function of the DOE is expressed as follows :
• Ci -1.13323-10
• intervals P k on the DOE at an incident point where a light ray for an angle of view of 0° are calculated as follows, as in Example 3, since the incident angle thereof is
• grating heights d k are as follows:
• FIG. 14 shows an optical system that collects each of two beams emitted from laser light sources 71a and 71b on a same image plane 74 by using a lens 73, the two beams being lights of mutually different wavelengths.
• An exit surface 731 of the lens 73 is provided with the transmissive laminated DOE of this example.
• E-FD8 is used as the light-transmissive medium for the first layer 41
• LAC14 is used as the light-transmissive medium for the second layer 42
• E-FD15 is used as the light- transmissive medium for the third layer 43 (Those glasses are manufactured by HOYA corporation) .
• FIG. 15 shows dispersion characteristics of E-FD8, LAC14 and E-FD15.
• An entrance pupil has a diameter of 5mm.
• the surface (DOE substrate surface) 2 is an aspheric surface (ASP) that is expressed by the following function:
• the surface 2 is a rotationally symmetric surface, and therefore the phase difference function of the DOE is expressed as follows:
• the coefficients C m of the grating surface 11 (for the wavelength ⁇ ) between the first second layers are set as follows:
• Cio 1.51900-10 "9 .
• the present invention can provide a laminated diffractive optical element with reduced chromatic aberration generated due to diffraction while having a strong power.

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Diffracting Gratings Or Hologram Optical Elements (AREA)
• Lenses (AREA)
• Optical Elements Other Than Lenses (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

Family

ID=43900195

Family Applications (1)

Country Status (5)

Cited By (1)

Families Citing this family (32)

Citations (2)

Family Cites Families (25)

• 2009
  • 2009-10-21 JP JP2009241989A patent/JP5059079B2/ja not_active Expired - Fee Related
• 2010
  • 2010-10-05 WO PCT/JP2010/067807 patent/WO2011048967A1/en active Application Filing
  • 2010-10-05 EP EP12187153A patent/EP2544038A3/en not_active Withdrawn
  • 2010-10-05 EP EP10824816A patent/EP2491441A4/en not_active Withdrawn
  • 2010-10-05 CN CN201080046745.1A patent/CN102597821A/zh active Pending
  • 2010-10-05 US US13/503,175 patent/US8885254B2/en not_active Expired - Fee Related

Patent Citations (2)

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events